The present invention relates to a method of regulating the idling rotational speed of an internal combustion engine and to an arrangement for performing such method.
There are already known, for instance, from the U.S. Pat. No. 4,444,471 and from U.S. Pat. No. 4,513,711, systems for the regulation of the idling rotational speed of internal combustion engines, which are also known as so called idling operation filling regulation devices or arrangements. The known systems for the idling operation filling regulation usually comprise, independently or whether are implemented in analog technology utilizing discrete swiching components or switching blocks, or are implemented in a digitized manner and with digital processing utilizing microprocessors, microcomputers and similar digitally operating devices, a regulation region which compares the actual rotational speed or number of revolutions per minute with a predetermined nominal or desired rotational speed and, in dependence on the regulation deviation or error signal, provides a manipulated variable which acts on an idling operation adjustment device which is constructed in a certain way, for instance, as a two-winding rotational adjuster. Herein, the regulation region can be constructed, solely or in combination, to exhibit a proportional, integral and/or differential behavior. The overall idling operation filling regulating arrangement may additionally also include an internal control loop in which, for instance for the adaptation of the adjustment member characteristic behavior, the desired intake air amount is additionally compared with the actual intake air amount or the actual and desired values of the intake pipe pressure are compared with one another. In the final effect, the idling operation adjustment member acts on the available flow-through cross-sectional area in the intake pipe of the respective internal combustion engine, especially by a corresponding increase or decrease of a bypass cross-sectional area or by a mechanical adjustment of the position of a throttling valve or damper.
In the U.S. Pat. No. 4,513,711, there is already addressed the problem, which is encountered in internal combustion engines equipped with idling operation regulation, of tendency toward jerky operation at the idling speeds. This problem results from the fact that, at certain proportions of the fuel/air mixture supplied to the internal combustion engine and/or during certain driving conditions, there come into being rotational speed oscillations or swings which can also be characterized as idling operation sawteeth and which, besides causing an unpleasant jerky operation or motion of the vehicle, can under certain circumstances become so pronounced or enhanced that the internal combustion engine stalls. Especially motor vehicles with manual transmissions which are equipped with an idling operation filling regulation arrangement can have a tendency to operate in a jerky manner, and especially when the respective idling rotational speed regulating device preferably exhibits a proportional-intgral-differential behavior or response, but also when this device exhibits at least a proportional behavior, and when a short-lived gasoline pulse occurs with the transmission in gear and coupled to the engine, for instance.
Another possibility of a jerky operation or motion in the idling operation region of the internal combustion engine can also result when the idling operation filling regulation device is not being used merely for the maintenance of a predetermined idling rotational speed of the engine in idle, but rather is used, for instance, when driving in a convoy or in the so-called stop-and-go traffic, for powering the vehicle. This possibility readily presents itself to the driver under certain circumstances, inasmuch as the idling operation filling regulation device attempts in each instance, to prevent stalling of the engine and to maintain the engine at or close to a predetermined, relatively low, idling operation rotational speed. During such use of the internal combustion engine under load conditions, but at the idling rotational speed, the regulation or control characteristic and behavior is naturally drastically changed, inasmuch as the idling operation filling regulation is so-to-say misused as compared with its intended use for which it has been designed. While it would be possible in this connection to take into account the possibility of switching the regulating or control parameters of the idling operation filling device in dependence on and in response to this operational condition to other, coordinated and appropriate, values, such a possibility is prohibitive, since an information about the coupling of the engine with the transmission train of the vehicle is either not available at all, or can be obtained only in a laborious way.
On the other hand, if one falls back, as a way out of this predicament, on the use of relatively slow regulation or control parameters for the idling operation filling regulation, then the overall regulation behavior becomes problematical, inasmuch as the idling operation filling regulation is provided, in accordance with its very nature, for the purpose of detecting and counteracting possibly occurring interventions into or changes in the rotational speed as quickly as possible and feasible. Thus, exactly in particularly quickly responding regulating devices operative in the area of idling operation filling regulation, the danger of occurrence of pronounced jerky oscillations is particularly apparent, possibly also since the mixture is too lean and operation skips or interruptions occur.